Nuclear magnetic resonance study of the molecular and electronic structure of the stable green sulfhemin prosthetic groups extracted from sulfmyoglobin

Chatfield, Mariann J.; Mar, Gerd N. La; Parker, Wallace O.; Smith, Kevin M.; Leung, Hiu-Kwong; Morris, Ian K.

doi:10.1021/ja00227a013

Cited by 36 publications

(21 citation statements)

References 1 publication

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“…SCMb is the most stable of these derivatives and has been suggested by subsequent NMR studies to possess a prosthetic group with a structure similar to that shown in Fig. 1 (17)(18)(19). Additional NMR experiments have yielded a spatial configuration for the heme substituents that is consistent with this model and that predicts the absolute configuration of the resulting chiral center about carbon atom C2C (20).…”

supporting

confidence: 53%

Three-dimensional structure of cyanomet-sulfmyoglobin C.

Evans

Sishta²,

Mauk³

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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The atomic structure of horse heart cyanomet-sulfmyoglobin C has been establied by x-ray crystalographic techniques to a resolution of 2.0 A with an R value of 0.129. The protoheme IX prosthetic group of this thermodynamically stable sulfnyoglobin derivative has been converted to a chlorin in which the pyrrole ring bearing the 4-vinyl group is saturated and possesses an exocyclic thiolene ring. This study provides the three-dimensional structure of a protein with an iron-chlorin prosthetic group. The overall conformation of the surrounding polypeptide chain of the modified protein is very similar to that of the native protein. However, the addition of the sufuratom has caused a distortion of the prosthetic group from that in the native protein to result in the repositioning of the side chains of some residues in the heme pocket.

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supporting

confidence: 53%

Three-dimensional structure of cyanomet-sulfmyoglobin C.

Evans

Sishta²,

Mauk³

et al. 1994

Proc. Natl. Acad. Sci. U.S.A.

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“…Usually the π-delocalization of unpaired spin density in metalloporphyrins is described in terms of ligand-to-metal and metal-to-ligand charge transfer . Spin densities at the particular carbons are related to the pattern of the occupied 3e(π) and unoccupied 4e*(π) molecular orbitals. ,,− Here, the Hückel calculations have been carried out for the quinoxalinoporphyrin dianion . The idealized geometry of the dianion has been used.…”

Section: Resultsmentioning

confidence: 99%

Characterization of High-Spin and Low-Spin Iron(III) Quinoxalinotetraphenylporphyrin

1997

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The 1H NMR spectra of iron(III) quinoxalinotetraphenylporphyrin ((QTPP)FeIIIX n ), iron(III) (methylquinoxalino)tetraphenylporphyrin ((MQTPP)FeIIIX n ), and iron(III) pyrazinotetraphenylporphyrin ((PTPP)FeIIIX n ) have been studied to elucidate the impact of an aromatic extension of a single pyrrole ring on the electronic structure of the corresponding high- and low-spin iron(III) porphyrins. The 1H NMR spectra of the complexes with the following axial ligands have been reported: chloride, iodide, cyanide, pyridine-d 5 (py-d 5), 4-aminopyridine (4-NH2py), and imidazole (ImH). Modification of the tetraphenylporphyrin by addition of the quinoxaline (pyrazine) fragment results in stabilization of the rare low-spin iron(III) (d xz d yz )4(d xy )1 electronic ground state in the presence of axial cyanide or pyridine ligands. The more common (d xy )2(d xz d yz )3 electronic ground state has been established for [(QTPP)FeIII(4-NH2py)2]+ and [(QTPP)FeIII(ImH)2]+ species. To account for the substituent contribution, the Hückel linear combination of atomic orbitals (LCAO) method has been used to determine the molecular orbitals involved in the spin density delocalization. The deviation from Curie law observed for [(QTPP)FeIII(CN)2]- suggests Boltzmann equilibrium {(d xz )2(d yz )2(d xy )2(Ψ- 1)1 ↔ (d xz )2(d yz )2(d xy )1(Ψ- 1)2} ⇌ (d xz )1(d yz )2(d xy )2(Ψ- 1)2 ⇌ (d xz )2(d yz )1(d xy )2(Ψ- 1)2 where Ψ- 1 is related to the a2u orbital of a regular porphyrin. For the first time in the group of low-spin iron(III) tetraarylporphyrins, the sign reversal of the isotropic shift was directly observed for pyrrole-proton resonances. The structure of (QTPP)FeIIICl was determined by X-ray crystallography. (QTPP)FeIIICl crystallizes in the monoclinic space group P21/c with a = 18.016(5) Å, b = 11.399(3) Å, c = 21.996(5) Å, β = 112.22(5)°, and Z = 4. The refinement of 548 parameters and 2696 reflections yields R 1 = 0.0654, R w2 = 0.1717. The (QTPP)FeIIICl presents features of the high-spin five-coordinate iron(III) tetraphenylporphyrin. The quinoxalinotetraphenylporphyrin macrocycle assumes a saddle-shape geometry.

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“…Increased relaxation rates for paramagnetically influenced nuclei results in very small NOE signal intensities. However, with the use of a viscous solvent (in this case a Me 2 SO-d 6 /D 2 O mixture at low temperatures), NOE enhancement is achieved through an increase in the rotational correlation time of the molecule, and thus an increase in crossrelaxation between nearby protons (30,31). To further enhance the possibility of NOE detection, the resonances selected for saturation were those with the smallest T 1 values of expected NOE pairs so that resulting NOEs could be detected on resonances with the slowest relaxation rates.…”

Section: Isolation and Identification Of Lpo Heme Species-severalmentioning

confidence: 99%

The Heme Prosthetic Group of Lactoperoxidase

Rae

Goff

1998

Journal of Biological Chemistry

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The heme prosthetic group from the bovine milk enzyme lactoperoxidase (LPO), termed heme l, is isolated through an approach that combines proteolytic hydrolysis and reverse-phase high performance liquid chromatographic separation of the resulting digest. Application of different proteases yields either a peptide-bound heme (with trypsin and chymotrypsin) or a peptide-free heme (with proteinase K). Both heme l and heme l-peptide species were investigated by paramagnetic

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Nuclear magnetic resonance study of the molecular and electronic structure of the stable green sulfhemin prosthetic groups extracted from sulfmyoglobin

Cited by 36 publications

References 1 publication

Three-dimensional structure of cyanomet-sulfmyoglobin C.

Three-dimensional structure of cyanomet-sulfmyoglobin C.

Characterization of High-Spin and Low-Spin Iron(III) Quinoxalinotetraphenylporphyrin

The Heme Prosthetic Group of Lactoperoxidase

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